Exploration and production of hydrocarbons generally requires that a borehole be drilled deep into the earth. The borehole provides access to a geologic formation that may contain a reservoir of oil or gas.
Drilling operations require many resources such as a drilling rig, a drilling crew, and support services. These resources can be very expensive. In addition, the expense can be even much higher if the drilling operations are conducted offshore. Thus, there is an incentive to contain expenses by drilling the borehole efficiently.
Efficiency can be measured in different ways. In one way, efficiency is measured by how fast the borehole can be drilled. Drilling the borehole too fast, though, can lead to problems. If drilling the borehole at a high rate-of-penetration results in a high probability of damaging equipment, then resources may be wasted in downtime and repairs. In addition, attempts at drilling the borehole too fast can lead to abnormal drilling events that can slow the drilling process.
There are many types of problems that can develop during drilling such as whirl and stick-slip. Stick-slip relates to the binding and release of the drill string while drilling and results in torsional oscillation of the drill string. Stick-slip can lead to damage to the drill bit and, in some cases, to failure of the drill string.
Mathematical models of the drilling system can be created. These models can be used to predict how changes in operating parameters/conditions (e.g., drilling speed, weight on bit, and the like) will affect the drilling process. In some cases, the models can be used by a model-based control system. It is understood that the models may need to be adapted as the system changes. For example, the drill string may experience changes in its physical properties, the bit may become dull, the properties of the drilling mud may change and the like. As such, model-based control systems perform better when constantly updated with actual conditions experienced while drilling. Actual conditions (measurements while drilling) are measured by tools in BHA (bottom hole assembly). The measurements can contain drillstring/BHA dynamics measurements.
One way to transfer actual conditions from a downhole location to the surface is to utilize mud-pulse telemetry. Mud-pulse telemetry is a common method of data transmission used by measurement while drilling tools. Such tools typically include a valve operated to restrict the flow of the drilling mud (slurry) according to the digital information to be transmitted. This creates pressure fluctuations representing the information. The pressure fluctuations propagate within the drilling fluid towards the surface where they are received by pressure sensors. Another way to transfer information may be to utilize an electromagnetic (EM) telemetry system.
In some cases, however, the bandwidth of EM and mudpulse telemetry systems may not be sufficient to provide all of the data required by the models in a timely manner. In some cases a wired pipe is utilized instead as a telemetry system. Wired pipes provide much greater bandwidth than mud-pulse telemetry systems but are expensive and less reliable.